Storylines, key matchups, predictions and more for the Bears vs. 49ers game Sunday at Soldier Field (noon, CBS).

4 storylines

Losing streak stopper? On the heels of the Bears’ worst loss in quarterback Mitch Trubisky’s young career – and a four-game losing streak — the 1-10 49ers roll into town to potentially provide some relief. The Bears netted just six yards on the ground against the Eagles, but they now face a 49ers defense that has given up 129.5 yards rushing per game, third worst in the NFL. Their pass defense has allowed 244.6 yards per game, seventh worst. It appears a prime opportunity for a confidence boost. “We have to run the ball, we have to control the line of scrimmage, and we have to be better on third down,” Trubisky said.

Jimmy G. comes home: Rolling Meadows and Eastern Illinois product Jimmy Garoppolo will play his first game at Soldier Field on Sunday when he makes his first start for the 49ers. It’s his first NFL start since filling in for the Patriots when Tom Brady was suspended last fall, and it comes a little more than a month after the 49ers traded a second-round draft pick to acquire him. 49ers coach Kyle Shanahan said it will take time before Garoppolo has a mastery of the offense. “Things are starting to slow down for me,” Garoppolo said. “It has been a process, but I think things are really coming together.”

The injury shuffle: Bears inside linebacker Danny Trevathan missed three November games, and the Bears defense stumbled in three losses. Trevathan, back at practice this week, could be a big boost, but each week seems to come with an injury to another starter. The Bears now are scrambling at safety after Adrian Amos went down Sunday. Will the Bears turn to Deon Bush, who himself is dealing with an ankle injury, Deiondre Hall or Chris Prosinski? “We have a bunch of guys who are hobbled and are not sure of their status,” Bears defensive coordinator Vic Fangio said. “I’m not really sure how that will shake itself out.”

Gould standard: Veteran 49ers kicker Robbie Gould returns to play in Chicago for the first time since the Bears cut him right before last season after 11 years with the team. He says he harbors no ill will to the organization, but he also admitted he was too emotional when he played the Bears in 2016 while with the Giants, missing two extra-point attempts. How will the Bears’ all-time leading scorer fare this time? And will new Bears kicker Cairo Santos be able to pull off a clean performance in his home debut? “I’m pretty excited to be in front of the fans, I’m not going to lie,” Gould said. “I love the fans. I love the organization.”

— Colleen Kane

Bears-49ers matchups

Bears on offense

In the air

NFL rank: Bears offense 31st, 49ers defense 26th

Rookie quarterback Mitch Trubisky is coming off his worst game. Mechanical breakdowns contributed to the passing game’s disjointedness. He was critical of his footwork, saying he faded away on some throws and didn’t step directly at his target on others. He also was bouncy in the upper body, not keeping his head still, offensive coordinator Dowell Loggains said. Both the 49ers’ first-string safeties — Jimmie Ward and Jaquiski Tartt — are on injured reserve, leaving a pedestrian secondary in place. First-round rookie end Solomon Thomas has only two sacks.

On the ground

NFL rank: Bears offense 8th, 49ers defense 30th

The Bears must control the line of scrimmage after the Eagles dominated last Sunday. The Bears lost too many individual blocks and couldn’t run the outside zone effectively because of how wide the Eagles positioned their defensive ends. Don’t be fooled by the 49ers total run defense ranking. They’re 10th in the league in yards per carry; the total is so high because they consistently play from behind. Linebacker Reuben Foster was the NFL’s defensive rookie of the month in November. He’s instinctive, fast and tracks the ball well.

Quarterback Jimmy Garoppolo makes his first start for the 49ers and only the third start of his career. He doesn’t have full command of the 49ers’ offense, but his athleticism and quick release are a starting point for the bootlegs they will run with him. Receivers Marquise Goodwin and Aldrick Robinson have dangerous deep speed. The Bears are depleted at safety after Adrian Amos (hamstring) was hurt against the Eagles and Deon Bush (ankle) went down in practice. Defensive lineman Akiem Hicks has gone three games without a sack.

On the ground

NFL rank: 49ers offense 23rd, Bears defense 16th

With a new quarterback, the 49ers will run their offense through Carlos Hyde. He runs hard and fast, and he has some wiggle, which makes him elusive. The 49ers operate a zone running game very similar to that of the Bears. After all, Dowell Loggains was the Browns quarterbacks coach in 2014 when 49ers coach Kyle Shanahan was their coordinator. Linebacker Danny Trevathan’s return from a three-game absence (calf strain) will help the tackling. But the Bears lack a run-stopping safety, given the latest round of injuries.

49ers 21st in total offense, 28th in points scored

Bears 12th in total defense, 15th in points allowed

— Rich Campbell

The assignment

Notable numbers: Hyde leads the 49ers in both rushing attempts (157) and catches (49) this season. The only other NFL player to lead his team in both categories is LeSean McCoy of the Bills with 192 carries and 46 receptions. … Trevathan led the Bears in tackles at the off week with 52 but has missed the last three games with a calf strain.

Scouting report: Hyde has been at the center of the 49ers’ offense under first-year coach Kyle Shanahan, averaging 19 touches per game and becoming a weapon as both a ball carrier and as a pass catcher. Shanahan praised Hyde’s durability this week, a plus for a running back who has been banged up frequently during his career. Shanahan has appreciated the way Hyde runs through arm tackles and has noted his improved ability running routes. Hyde is averaging 4.1 yards per carry this season but has had only one 100-yard rushing game — and that was a 125-yard output in Week 2. Still, his rugged running style will present a challenge to the Bears.

Word from within: “He’s a tough runner. He doesn’t shy away from contact. He’s big but still explosive. And they have been using him a lot. It’s going to be a challenge for us. But we’re up for it.” — Trevathan

— Dan Wiederer

Scouting report

Rookie Reuben Foster was elected 31st overall after the 49ers traded into the back end of the first round to select the 6-foot-1, 228-pound Alabama product. He’s tied for sixth on the team with 38 tackles but missed five games with a high ankle sprain suffered in the opener and a sixth with a rib injury.

Despite only three games for the 49ers in November, Foster was named the defensive rookie of the month as he had 30 tackles (14 in a Nov. 5 loss to the Cardinals) and 25 solo tackles. There were some injury concerns about Foster when he came out of Alabama, specifically a shoulder issue.

“Foster is amazingly physical. When he hits, he hits to put guys on IR,” the scout said. “That’s the best way to say it. He tries to put guys down, not just tackle them. He explodes to the ball and he can close short areas quickly. Looks like he is starting to develop a little more as a multi-level player.

“One of the concerns you had about him when he came out was whether or not he could be on the field on third down. I’m talking about have an impact on third downs. You had questions about him covering tight ends when needed and if he could match up on running backs coming out of the backfield because on third down he has to be more than just a downhill, physical thumper and that’s sort of a product of what he was asked to do at Alabama.

“We’re starting to see more of that. He has lateral speed and he can get sideline to sideline. He’s never going to be a Thomas Davis-type in terms of overall flexibility and change-of-direction skills, but he does some things Davis doesn’t do. He’s talented enough to get to the point when you’ll be able to match him up against a really good tight end on third down. The Bears don’t have a player that will worry San Francisco on third down in that way.

“He’s getting better at blitzing. He would velcro to guys at Alabama and try to run through everyone because he was stronger. That doesn’t work in the NFL. So he’s showing a little better technique. He just has to be on the field more, he has missed a bunch of time. He will be a good player, maybe really good but the idea San Francisco was comfortable taking this kid at No. 3, which the 49ers tried to sell right after the draft? No way. He’s not Luke Kuechly.”

— Brad Biggs

Bears-49ers predictions

Brad Biggs (6-5)

49ers will get close-up look at player Bears had to have on draft night. If Bears can get ground game going, Mitch Trubisky should have chance to make plays — and he needs to. Bears 24, 49ers 23

Rich Campbell (7-4)

For Bears to maintain cohesion in final month, they can’t afford to lose at home to a 1-10 opponent. They’ll win Sunday because they’re still playing hard, and they’re better than the 49ers, who have similar talent deficiencies. Bears must get back to running and controlling the line of scrimmage offensively after Eagles dominated them. That would help open passing game for Mitch Trubisky and lackluster receiving corps, which should be able to take advantage of the 49ers’ pedestrian secondary. Defensively, Bears must capitalize on Jimmy Garoppolo’s inexperience by forcing him to play from the pocket and read the field. Bears 20, 49ers 13

Colleen Kane (6-5)

How will Jimmy Garoppolo fare in third NFL start? It doesn’t help Bears their defense loses a starter to injury nearly every week. But offense, especially running game, should look much better than in Eagles debacle. Bears 24, 49ers 17

Mike Mulligan (5-6)

Drop in class from Eagles to 49ers, coupled with return home, should make difference. It would be much easier if Jimmy Garoppolo wasn’t starting, but if Bears ever are going to win again it’s here. Bears 21, 49ers 17

Phil Thompson (6-5)

A quarterback change. Devastating defensive injuries. Mediocre receivers. Bears and 49ers look so much alike they even have identical yards per play (4.9) and turnover differential ( minus-4). This is the kind of game Bears should win easily, which means they probably will lose. The game-winner likely comes down to a Robbie Gould kick. 49ers 24, Bears 23

Dan Wiederer (9-2)

On a five-game December slate, this registers as one of two must-wins for the Bears. Only two teams have fewer victories since the start of 2015. The 49ers are one of them. Get excited, sports fans. It may not be a pretty game at Soldier Field. But a home loss to a 1-10 squad would be another major embarrassment for an organization that can ill afford that. So can John Fox keep his sputtering team from letting dejection take over? Can the defense deliver a spirited effort against new 49ers QB Jimmy Garoppolo? Can Mitch Trubisky propel the Bears to a needed victory? The Bears better hope so. Bears 24, 49ers 20